text: /*
   * This file is part of the GROMACS molecular simulation package.
   *
   * Copyright 1991- The GROMACS Authors
   * and the project initiators Erik Lindahl, Berk Hess and David van der Spoel.
   * Consult the AUTHORS/COPYING files and https://www.gromacs.org for details.
   *
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   * as published by the Free Software Foundation; either version 2.1
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   */
  #ifndef GMX_TOPOLOGY_IFUNC_H
  #define GMX_TOPOLOGY_IFUNC_H
  
  #include "gromacs/math/vectypes.h"
  
  struct t_fcdata;
  struct t_graph;
  union t_iparams;
  struct t_mdatoms;
  struct t_pbc;
  
  /* TODO: Remove this typedef when t_ilist is removed */
  typedef int t_iatom;
  
  /* Real vector type with an additional, unused 4th element.
   * This type is used to allow aligned 4-wide SIMD loads and stores.
   */
  typedef real rvec4[4];
  
  /*
   * The function type t_ifunc() calculates one interaction, using iatoms[]
   * and iparams. Within the function the number of atoms to be used is
   * known. Within the function only the atomid part of the iatoms[] array
   * is supplied, not the type field (see also t_ilist). The function
   * returns the potential energy. If pbc==NULL the coordinates in x are
   * assumed to be such that no calculation of PBC is necessary,
   * If pbc!=NULL a full PBC calculation is performed.
   * If g!=NULL it is used for determining the shift forces.
   * With domain decomposition ddgatindex can be used for getting global
   * atom numbers for warnings and error messages.
   * ddgatindex is NULL when domain decomposition is not used.
   */
  
  constexpr unsigned int IF_NULL       = 0;
  constexpr unsigned int IF_BOND       = 1 << 0;
  constexpr unsigned int IF_VSITE      = 1 << 1;
  constexpr unsigned int IF_CONSTRAINT = 1 << 2;
  constexpr unsigned int IF_CHEMBOND   = 1 << 3;
  constexpr unsigned int IF_BTYPE      = 1 << 4;
  constexpr unsigned int IF_ATYPE      = 1 << 5;
  constexpr unsigned int IF_DIHEDRAL   = 1 << 6;
  constexpr unsigned int IF_PAIR       = 1 << 7;
  constexpr unsigned int IF_TABULATED  = 1 << 8;
  constexpr unsigned int IF_LIMZERO    = 1 << 9;
  /* These flags tell to some of the routines what can be done with this
   * item in the list.
   * With IF_BOND a bonded interaction will be calculated.
   * With IF_BTYPE grompp can convert the bond to a Morse potential.
   * With IF_BTYPE or IF_ATYPE the bond/angle can be converted to
   * a constraint or used for vsite parameter determination by grompp.
   * IF_LIMZERO indicates that for a bonded interaction the potential
   * does goes to zero for large distances, thus if such an interaction
   * it not assigned to any node by the domain decompostion, the simulation
   * still continue, if mdrun has been told so.
   */
  
  struct t_interaction_function // NOLINT (clang-analyzer-optin.performance.Padding)
  {
      const char* name;         /* the name of this function			*/
      const char* longname;     /* The name for printing etc.                   */
      int         nratoms;      /* nr of atoms needed for this function		*/
      int         nrfpA, nrfpB; /* number of parameters for this function.      */
                                /* this corresponds to the number of params in  */
                                /* iparams struct! (see idef.h)                 */
      /* A and B are for normal and free energy components respectively.    */
      unsigned int flags; /* Flags (see above)                            */
  };
  
  #define NRFPA(ftype) (interaction_function[(ftype)].nrfpA)
  #define NRFPB(ftype) (interaction_function[(ftype)].nrfpB)
  #define NRFP(ftype) (NRFPA(ftype) + NRFPB(ftype))
  #define NRAL(ftype) (interaction_function[(ftype)].nratoms)
  
  #define IS_CHEMBOND(ftype) \
      (interaction_function[(ftype)].nratoms == 2 && (interaction_function[(ftype)].flags & IF_CHEMBOND))
  /* IS_CHEMBOND tells if function type ftype represents a chemical bond */
  
  /* IS_ANGLE tells if a function type ftype represents an angle
   * Per Larsson, 2007-11-06
   */
  #define IS_ANGLE(ftype) \
      (interaction_function[(ftype)].nratoms == 3 && (interaction_function[(ftype)].flags & IF_ATYPE))
  #define IS_VSITE(ftype) (interaction_function[(ftype)].flags & IF_VSITE)
  
  #define IS_TABULATED(ftype) (interaction_function[(ftype)].flags & IF_TABULATED)
  
  /* this MUST correspond to the
     t_interaction_function[F_NRE] in gmxlib/ifunc.cpp */
  enum
  {
      F_BONDS,
      F_G96BONDS,
      F_MORSE,
      F_CUBICBONDS,
      F_CONNBONDS,
      F_HARMONIC,
      F_FENEBONDS,
      F_TABBONDS,
      F_TABBONDSNC,
      F_RESTRBONDS,
      F_ANGLES,
      F_G96ANGLES,
      F_RESTRANGLES,
      F_LINEAR_ANGLES,
      F_CROSS_BOND_BONDS,
      F_CROSS_BOND_ANGLES,
      F_UREY_BRADLEY,
      F_QUARTIC_ANGLES,
      F_TABANGLES,
      F_PDIHS,
      F_RBDIHS,
      F_RESTRDIHS,
      F_CBTDIHS,
      F_FOURDIHS,
      F_IDIHS,
      F_PIDIHS,
      F_TABDIHS,
      F_CMAP,
      F_GB12_NOLONGERUSED,
      F_GB13_NOLONGERUSED,
      F_GB14_NOLONGERUSED,
      F_GBPOL_NOLONGERUSED,
      F_NPSOLVATION_NOLONGERUSED,
      F_LJ14,
      F_COUL14,
      F_LJC14_Q,
      F_LJC_PAIRS_NB,
      F_LJ,
      F_BHAM,
      F_LJ_LR_NOLONGERUSED,
      F_BHAM_LR_NOLONGERUSED,
      F_DISPCORR,
      F_COUL_SR,
      F_COUL_LR_NOLONGERUSED,
      F_RF_EXCL,
      F_COUL_RECIP,
      F_LJ_RECIP,
      F_DPD,
      F_POLARIZATION,
      F_WATER_POL,
      F_THOLE_POL,
      F_ANHARM_POL,
      F_POSRES,
      F_FBPOSRES,
      F_DISRES,
      F_DISRESVIOL,
      F_ORIRES,
      F_ORIRESDEV,
      F_ANGRES,
      F_ANGRESZ,
      F_DIHRES,
      F_DIHRESVIOL,
      F_CONSTR,
      F_CONSTRNC,
      F_SETTLE,
      F_VSITE1,
      F_VSITE2,
      F_VSITE2FD,
      F_VSITE3,
      F_VSITE3FD,
      F_VSITE3FAD,
      F_VSITE3OUT,
      F_VSITE4FD,
      F_VSITE4FDN,
      F_VSITEN,
      F_COM_PULL,
      F_DENSITYFITTING,
      F_EQM,
      F_EPOT,
      F_EKIN,
      F_ETOT,
      F_ECONSERVED,
      F_TEMP,
      F_VTEMP_NOLONGERUSED,
      F_PDISPCORR,
      F_PRES,
      F_DVDL_CONSTR,
      F_DVDL,
      F_DKDL,
      F_DVDL_COUL,
      F_DVDL_VDW,
      F_DVDL_BONDED,
      F_DVDL_RESTRAINT,
      F_DVDL_TEMPERATURE, /* not calculated for now, but should just be the energy (NVT) or enthalpy (NPT), or 0 (NVE) */
      F_NRE /* This number is for the total number of energies      */
  };
  
  static inline bool IS_RESTRAINT_TYPE(int ifunc)
  {
      return ifunc == F_POSRES || ifunc == F_FBPOSRES || ifunc == F_DISRES || ifunc == F_RESTRBONDS
             || ifunc == F_DISRESVIOL || ifunc == F_ORIRES || ifunc == F_ORIRESDEV
             || ifunc == F_ANGRES || ifunc == F_ANGRESZ || ifunc == F_DIHRES;
  }
  
  /* Maximum allowed number of atoms, parameters and terms in interaction_function.
   * Check kernel/toppush.c when you change these numbers.
   */
  constexpr int MAXATOMLIST   = 6;
  constexpr int MAXFORCEPARAM = 12;
  constexpr int NR_RBDIHS     = 6;
  constexpr int NR_CBTDIHS    = 6;
  constexpr int NR_FOURDIHS   = 4;
  
  extern const t_interaction_function interaction_function[F_NRE];
  /* initialised interaction functions descriptor				*/
  
  #endif
  